Ok, so this is a bit embarrassing.

I have seen people comment that they wear tank tops "for layering." What exactly does that mean?

In my world that's what a camisole was for--well, actually, it as the piece you wore under a see-through blouse (not that you had one. Inappropriate, really, so I was always told, so I have never had one nor needed one.) As well, anything so low cut as to need something underneath it was put back on the rack and something more modest would be chosen. I never had a problem with that--why would you buy something--oly to buy something else just so you could wear it? Didn't make much sense to practical ol' me.

A tank top was just for wearing on hot days with shorts.

Obviously, I am missing something!

Teach me, please. Thanks!